linux-kernel - Re: [RESEND] [PATCH] readahead:add blk_run_backing

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Message-ID: <a0272b440907130547x2fb6fbc6g4764e61cb7ba9fff@mail.gmail.com>
Date:	Mon, 13 Jul 2009 14:47:31 +0200
From:	Ronald Moesbergen <intercommit@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Vladislav Bolkhovitin <vst@...b.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"Alan.Brunelle@...com" <Alan.Brunelle@...com>,
	"hifumi.hisashi@....ntt.co.jp" <hifumi.hisashi@....ntt.co.jp>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	Bart Van Assche <bart.vanassche@...il.com>
Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

2009/7/13 Wu Fengguang <fengguang.wu@...el.com>:
> On Mon, Jul 13, 2009 at 08:12:14PM +0800, Ronald Moesbergen wrote:
>> 2009/7/10 Vladislav Bolkhovitin <vst@...b.net>:
>> >
>> > Vladislav Bolkhovitin, on 07/10/2009 12:43 PM wrote:
>> >>
>> >> Ronald Moesbergen, on 07/10/2009 10:32 AM wrote:
>> >>>>
>> >>>> I've also long ago noticed that reading data from block devices is
>> >>>> slower
>> >>>> than from files from mounted on those block devices file systems. Can
>> >>>> anybody explain it?
>> >>>>
>> >>>> Looks like this is strangeness #2 which we uncovered in our tests (the
>> >>>> first
>> >>>> one was earlier in this thread why the context RA doesn't work with
>> >>>> cooperative I/O threads as good as it should).
>> >>>>
>> >>>> Can you rerun the same 11 tests over a file on the file system, please?
>> >>>
>> >>> I'll see what I can do. Just te be sure: you want me to run
>> >>> blockdev-perftest on a file on the OCFS2 filesystem which is mounted
>> >>> on the client over iScsi, right?
>> >>
>> >> Yes, please.
>> >
>> > Forgot to mention that you should also configure your backend storage as a
>> > big file on a file system (preferably, XFS) too, not as direct device, like
>> > /dev/vg/db-master.
>>
>> Ok, here are the results:
>
> Ronald, thanks for the numbers!

You're welcome.

>> client kernel: 2.6.26-15lenny3 (debian)
>> server kernel: 2.6.29.5 with readahead patch
>
> Do you mean the context readahead patch?

No, I meant the blk_run_backing_dev patch. The patchnames are
confusing, I'll be sure to clarify them from now on.

Ronald.
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